Ceramic riser tube for vacuum low-pressure casting of high-temperature alloy and preparation method of ceramic riser tube

Abstract

The invention belongs to the technical field of low-pressure anti-gravity casting, and particularly relates to a ceramic riser tube for high-temperature alloy vacuum low-pressure casting and a preparation method of the ceramic riser tube. The aggregate comprises the following components in parts by weight: 10-20 parts of alumina powder particles, 15-25 parts of alumina fine powder particles, 30-50 parts of fused quartz powder and 15-30 parts of fused quartz fine powder; the powder material comprises 1-5 parts of silica fume, 3-5 parts of a binding agent, 0.4 part of a dispersing agent and 0.01-0.05 part of boric acid; the amount of the ionized water is 10 to 15 parts; wherein the diameter of the alumina powder particles is 5 [mu] m, and the diameter of the alumina fine powder particles is 0.5 [mu] m. The ceramic riser tube provided by the invention adopts the aluminum oxide matrix, so that the thermal shock resistance is excellent, meanwhile, the riser tube does not react with high-temperature alloy molten metal in the casting process, and the purity of the molten metal can be ensured. The riser tube manufactured through the method is high in size precision, the production process is simple and convenient, and low-cost and large-batch production can be achieved.

Description

Technical Field

[0001] The invention belongs to the technical field of low-pressure counter-gravity casting, and in particular relates to a ceramic riser tube for vacuum low-pressure casting of high-temperature alloys and a preparation method thereof. Background Art

[0002] At present, ceramic riser tubes are mainly used for casting aluminum alloys and magnesium alloys. Low-pressure counter-gravity casting is a melting and casting process that uses pressure to make the molten metal fill the mold from bottom to top in the opposite direction of gravity. According to the different forms of pressure applied when the molten metal fills the mold, counter-gravity casting can be divided into low-pressure casting, differential pressure casting, pressure-adjusting casting and vacuum suction casting. The riser tube is one of the key components of counter-gravity casting. When filling the mold, under the action of air pressure, the molten metal enters the mold from the crucible through the riser tube. When the pressure is released, the unsolidified molten metal also flows back to the crucible through the riser tube. Counter-gravity casting was used in the production of castings such as copper sleeves and automobile aluminum alloy wheels in the early days. With the development of aircraft engines and gas turbines, the quality requirements for casting products have been continuously improved. The application scope of low-pressure counter-gravity has begun to expand from low-melting-point alloys such as aluminum alloys and magnesium alloys to high-melting-point alloys such as cast iron, cast steel, and high-temperature alloys.

[0003] Compared with high-temperature alloys, high-temperature alloys have the characteristics of high density, high melting point, and high alloy density, which means that the riser tube needs to withstand more severe working conditions during the high-temperature alloy filling process and needs to have better high-temperature strength, better thermal shock resistance, and air tightness. There is still little research on ceramic riser tubes for high-temperature alloys in China, and there will be great room for development in the research and development and application of such riser tubes.

[0004] Chinese patent CN117532725A discloses a method for preparing a ceramic riser tube for high-temperature alloys. The process uses a refractory slurry / sand layer-by-layer coating process to make a shell on a 3D printed wax model. The produced riser tube is similar to the shell used for investment casting, and is a multi-layer structure with good high-temperature strength and air tightness. However, this process is not suitable for mass production because it has many steps and the 3D printed wax model is prone to deformation if it is not properly stored.

[0005] Chinese patent CN109940152B discloses a riser tube for high-temperature alloy anti-gravity casting, which uses a metal tube with a convex structure as a skeleton, and uses refractory materials and refractory fibers to coat the surface of the metal tube for vacuum anti-gravity casting of high-temperature alloys. The preparation process of the riser requires coating the surface of the metal skeleton layer by layer, which requires high costs and low production efficiency. In addition, the riser tube prepared by the patent has poor thermal shock resistance, and the refractory material is easily separated from the metal skeleton during use, and can only meet the use requirements in a short period of time.

[0006] Therefore, it is necessary to develop a new ceramic riser tube and a preparation method thereof. Summary of the invention

[0007] The invention discloses a ceramic riser tube for vacuum low-pressure casting of high-temperature alloys and a preparation method thereof, so as to prepare a ceramic riser tube with good thermal stability and excellent thermal shock resistance.

[0008] To achieve the above object, the present invention adopts the following specific technical scheme: a ceramic riser tube for vacuum low-pressure casting of high-temperature alloy, the raw materials for making the ceramic riser tube include aggregate, powder and deionized water;

[0009] In terms of weight, the aggregate comprises: 10-20 parts of alumina powder particles, 15-25 parts of alumina fine powder particles, 30-50 parts of fused quartz powder, and 15-30 parts of fused quartz fine powder;

[0010] The powder material includes 1-5 parts of silica fume, 3-5 parts of binder, 0.4 parts of dispersant, 0.01-0.05 parts of boric acid; the ionized water is 10-15 parts;

[0011] The diameter of the aluminum oxide powder particles is 5 μm, and the diameter of the aluminum oxide fine powder particles is 0.5 μm.

[0012] A method for preparing a ceramic riser tube for vacuum low-pressure casting of high-temperature alloys comprises the following steps:

[0013] Step 1: preparing aggregate: according to weight parts, obtain 10-20 parts of alumina powder particles, 15-25 parts of alumina fine powder particles, 30-50 parts of fused quartz powder, and 15-30 parts of fused quartz fine powder, and mix them evenly in a blender to obtain aggregate;

[0014] Step 2: Prepare powder: according to weight parts, obtain 1-5 parts of silica fume, 3-5 parts of binder, 0.4 parts of dispersant, and 0.01-0.05 parts of boric acid, mix them evenly in a blender to obtain powder;

[0015] Step 3: Prepare slurry: add powder to aggregate, mix well, add 10-15 parts of deionized water in batches, and stir to form slurry;

[0016] Step 4: The slurry obtained in step 3 is sent to a vacuum mixer to remove bubbles in the slurry for later use;

[0017] Step 5: pour the defoamed slurry into the mold cavity;

[0018] Step 6: Demolding and drying: After the slurry hardens, take it out of the mold, and place the riser tube embryo in an oven for drying;

[0019] Step 7: Sintering of the riser tube embryo: placing the dried riser tube embryo in a push-plate kiln furnace, and sintering to obtain a ceramic riser tube for vacuum low-pressure casting of high-temperature alloys.

[0020] Furthermore, in step 1, the particle diameter of the fused quartz powder is 0.3-1 mm, and the particle diameter of the fused quartz fine powder is 0-0.3 mm; and the mixing time for preparing the aggregate in the mixer is 10-15 min.

[0021] Furthermore, the binder in step 2 is gel powder; the dispersant is sodium tripolyphosphate; and the mixing time for preparing the powder in the mixer is 15-20 minutes.

[0022] Furthermore, in step 3, the aggregate is added to the powder and stirred for 5-10 minutes, and then deionized water is added in portions and stirred for 15-20 minutes.

[0023] Furthermore, in the defoaming process using a vacuum mixer in step 4, the vacuum degree is -0.1Mpa, and the vacuum defoaming time is 15-20 minutes.

[0024] Furthermore, in step 5, the mold is a silicone mold; the defoamed slurry is poured into the silicone mold cavity treated with a release agent, and a vibration tool is used to expel residual air in the mold cavity.

[0025] Furthermore, in step 6, the slurry is taken out from the mold after hardening, and the riser tube embryo is placed in an oven for drying, which specifically includes: placing the cast mold and the slurry in a constant temperature and humidity chamber for curing and hardening, and the temperature and humidity of the constant temperature and humidity chamber are 20-25°C and 40%-45% respectively; after the slurry is hardened, it is taken out from the mold, and the riser tube embryo is placed in an oven for drying, and the drying temperature is 110°C and the drying time is 20-30h.

[0026] Furthermore, in step 7, the sintering temperature of the riser tube embryo is 1000-1200°C.

[0027] The present invention can achieve the following technical effects:

[0028] The alumina ceramic matrix of the ceramic riser tube of the present invention has excellent high temperature resistance and can withstand extremely high temperatures during the smelting and pouring of high temperature alloys.

[0029] The alumina ceramic riser tube of the present invention has good chemical stability, has strong corrosion resistance to metal ions and slag in high-temperature alloy melt, and is not easy to react chemically with chemical components in the high-temperature alloy, thereby ensuring the purity of the alloy liquid;

[0030] The alumina ceramic riser tube of the invention patent is formed in one piece with a silicone mold, and the inner wall of the riser tube is smooth, which has little effect on the fluidity of the high-temperature alloy liquid. During use, the molten metal can rise at a relatively stable speed and state, reducing vortices and turbulence in the liquid, which can effectively improve the quality of the casting;

[0031] The riser tube manufactured by the present invention has high dimensional accuracy and simple production process, and can achieve low-cost and large-scale production. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the invention and, together with the description, serve to explain the principles of the invention.

[0033] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0034] Figure 1 The present invention is a flow chart of a method for preparing a ceramic riser tube;

[0035] Figure 2 It is a cross-sectional view of the silicone mold disclosed in the present invention;

[0036] Figure 3 is a cross-sectional view of the ceramic riser tube disclosed in the present invention;

[0037] Figure 4 The XRD spectrum of the ceramic riser tube disclosed in the present invention.

[0038] In the figure, 1 is the inner mold; 2 is the outer mold; 3 is the riser tube body; 4 is the flange. DETAILED DESCRIPTION

[0039] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and do not constitute a limitation of the present invention.

[0040] In order to solve the problems of poor thermal shock resistance and complex production process of existing ceramic riser tubes during use, this embodiment provides a ceramic riser tube for vacuum low-pressure casting of high-temperature alloys. Figure 1-4 , the raw materials for making the ceramic riser tube include aggregate, powder and deionized water;

[0041] In terms of weight, the aggregate comprises: 10-20 parts of alumina powder particles, 15-25 parts of alumina fine powder particles, 30-50 parts of fused quartz powder, and 15-30 parts of fused quartz fine powder;

[0042] The powder material includes 1-5 parts of silica fume, 3-5 parts of binder, 0.4 parts of dispersant, 0.01-0.05 parts of boric acid; the ionized water is 10-15 parts;

[0043] The diameter of the aluminum oxide powder particles is 5 μm, and the diameter of the aluminum oxide fine powder particles is 0.5 μm.

[0044] A method for preparing a ceramic riser tube for vacuum low-pressure casting of high-temperature alloys comprises the following steps:

[0045] Step 1: preparing aggregate: according to weight parts, obtain 10-20 parts of alumina powder particles, 15-25 parts of alumina fine powder particles, 30-50 parts of fused quartz powder, and 15-30 parts of fused quartz fine powder, and mix them evenly in a blender to obtain aggregate;

[0046] Furthermore, in step 1, the particle diameter of the fused quartz powder is 0.3-1 mm, and the particle diameter of the fused quartz fine powder is 0-0.3 mm; and the mixing time of the prepared aggregate in the mixer is 10-15 min.

[0047] Step 2: Prepare powder: according to weight parts, obtain 1-5 parts of silica fume, 3-5 parts of binder, 0.4 parts of dispersant, and 0.01-0.05 parts of boric acid, mix them evenly in a blender to obtain powder;

[0048] Furthermore, in step 2, the binder is gel powder; the dispersant is sodium tripolyphosphate; and the mixing time of the prepared powder in the mixer is 15-20 minutes.

[0049] Step 3: Prepare slurry: Add aggregate to powder and stir for 5-10 minutes, then add 10-15 parts of deionized water in batches and continue stirring for 15-20 minutes to form slurry.

[0050] Step 4: The slurry obtained in step 3 is sent to a vacuum mixer to remove bubbles in the slurry for later use;

[0051] Furthermore, in the defoaming process using a vacuum mixer in step 4, the vacuum degree is -0.1Mpa, and the vacuum defoaming time is 15-20 minutes.

[0052] Step 5: pouring the debubbled slurry into the mold cavity; specifically, the mold in step 5 is a silicone mold; pouring the debubbled slurry into the silicone mold cavity treated with a release agent, and using a vibration tool to expel residual air in the mold cavity.

[0053] It should be noted that the ceramic riser tube manufactured by the present invention is an integrated structure consisting of a riser tube body 3 and a flange 4 on the upper portion thereof; the riser tube body 3 is a circular tubular structure, and the flange 4 is a disc-shaped structure;

[0054] The silicone mold includes an inner mold 1 and an outer mold 2; the inner mold 1 and the outer mold 2 are snapped together and the outer mold 2 is mounted on the outside of the inner mold 1; the space between the inner mold 1 and the outer mold 2 serves as the cavity of the silicone mold; the structural shape of the cavity matches the shape of the riser tube body 3 and the flange 4 on its upper portion.

[0055] Step 6: Demolding and drying: Wait for the slurry to harden before taking it out from the mold, and then place the riser tube embryo in an oven for drying. Specifically, place the cast mold and slurry in a constant temperature and humidity chamber for curing and hardening. The temperature and humidity of the constant temperature and humidity chamber are 20-25°C and 40%-45%, respectively. After the slurry hardens, take it out from the mold, and then place the riser tube embryo in an oven for drying. The drying temperature is 110°C and the drying time is 20-30h.

[0056] Step 7: Sintering of the riser tube embryo: placing the dried riser tube embryo in a push-plate kiln at a sintering temperature of 1000-1200° C.; after sintering, a ceramic riser tube for vacuum low-pressure casting of high-temperature alloys is obtained.

[0057] A method for preparing an alumina ceramic riser tube for low-pressure counter-gravity casting of high-temperature alloys is provided in this embodiment. The prepared ceramic riser tube has stable chemical properties, and its main components are alumina and quartz, and has good thermal shock resistance.

[0058] Example 1

[0059] A ceramic riser tube for vacuum low-pressure casting of high-temperature alloys is prepared according to the following steps:

[0060] Step 1: Prepare aggregate: by weight, take 15 parts of 5μm alumina powder, 18 parts of 0.5μm alumina fine powder, 40 parts of fused quartz powder with a particle size of 0.3-1mm, and 27 parts of fused quartz fine powder with a particle size of 0-0.3mm, put them into a mixer, stir for 10 minutes, stir the aggregates thoroughly and evenly, and set aside;

[0061] Step 2: Prepare powder: Take 3 parts of silica fume, 0.02 parts of customized boric acid particles, 4 parts of binder, and 0.4 parts of dispersant by weight, put them into a blender, stir for 15 minutes, stir the powder thoroughly and evenly, and set aside;

[0062] Step 3: Prepare slurry: put the aggregate into the mixer, slowly add the powder during the mixing process, stir for 5 minutes to mix evenly, then add 10 parts of deionized water in batches, stir thoroughly for 15 minutes to form a uniform slurry;

[0063] Step 4: Vacuum degassing: put the slurry in step 4 into a vacuum mixer, and after the vacuum degree reaches -0.1Mpa, stir for 15 minutes to remove the bubbles generated by stirring in the slurry, and then seal and store for later use;

[0064] Step 5: Pour the defoamed slurry into the silicone mold cavity treated with a release agent, and vibrate it for 5 minutes using a vibration tool at the mold corner to expel the residual air in the mold cavity, so that the slurry is fully filled in the silicone mold and the surface is in a slurry state;

[0065] Step 6: demoulding and drying: the mold after casting is placed in an environment with a temperature and humidity of 25°C and 40% to cure and harden the slurry inside. After the slurry is hardened, it is taken out and the silicone mold is removed. The riser tube embryo is obtained and then placed in an oven at 110°C for 24 hours to dry and remove excess moisture inside the riser tube embryo.

[0066] Step 7: Sintering of the riser tube embryo: The dried riser tube embryo is placed in a push-plate kiln and sintered at 1100° C. to obtain a ceramic riser tube for vacuum low-pressure casting of high-temperature alloys.

[0067] Example 2

[0068] A ceramic riser tube for vacuum low-pressure casting of high-temperature alloys is prepared according to the following steps:

[0069] Step 1: Prepare aggregate: by weight, take 10 parts of 5 μm alumina powder, 23 parts of 0.5 μm alumina fine powder, 35 parts of fused quartz powder with a particle size of 0.3-1 mm, and 32 parts of fused quartz fine powder with a particle size of 0-0.3 mm, put them into a mixer, stir for 12 minutes, stir the aggregates thoroughly and evenly, and set aside;

[0070] Step 2: Prepare powder: Take 4 parts of silica fume, 0.04 parts of customized boric acid particles, 3 parts of binder, and 0.4 parts of dispersant by weight, put them into a blender, stir for 17 minutes, stir the powder thoroughly and evenly, and set aside;

[0071] Step 3: Prepare slurry: put the aggregate into the mixer, slowly add the powder during the mixing process, stir for 5 minutes to mix evenly, then add 12 parts of deionized water in batches, stir thoroughly for 17 minutes to form a uniform slurry;

[0072] Step 4: Vacuum degassing: put the slurry in step 4 into a vacuum mixer, and after the vacuum degree reaches -0.1Mpa, stir for 17 minutes to remove the bubbles generated by stirring in the slurry, and then seal and store for later use;

[0073] Step 5: Pour the defoamed slurry into the silicone mold cavity treated with a release agent, and vibrate it for 7 minutes using a vibration tool at the mold corner to expel the residual air in the mold cavity, so that the slurry is fully filled in the silicone mold and the surface is in a slurry state;

[0074] Step 6: demoulding and drying: the mold and slurry after casting are placed in an environment with a temperature and humidity of 20°C and 45% respectively to cure and harden the slurry. After the slurry is hardened, it is taken out and the silicone mold is removed. The riser tube embryo is obtained and then placed in an oven at 110°C for 20 hours to dry and remove excess moisture inside the riser tube embryo.

[0075] Step 7: Sintering of the riser tube embryo: The dried riser tube embryo is placed in a push-plate kiln and sintered at 1050° C. to obtain a ceramic riser tube for vacuum low-pressure casting of high-temperature alloys.

[0076] Example 3

[0077] A ceramic riser tube for vacuum low-pressure casting of high-temperature alloys is prepared according to the following steps:

[0078] Step 1: Prepare aggregate: by weight, take 20 parts of 5 μm alumina powder, 13 parts of 0.5 μm alumina fine powder, 30 parts of fused quartz powder with a particle size of 0.3-1 mm, and 37 parts of fused quartz fine powder with a particle size of 0-0.3 mm, put them into a mixer, stir for 10 minutes, stir the aggregates thoroughly and evenly, and set aside;

[0079] Step 2: Prepare powder: Take 5 parts of silica fume, 0.05 parts of customized boric acid particles, 3 parts of binder, and 0.4 parts of dispersant by weight, put them into a blender, stir for 20 minutes, stir the powder thoroughly and evenly, and set aside;

[0080] Step 3: Prepare slurry: put the aggregate into the mixer, slowly add the powder during the mixing process, stir for 5 minutes to mix evenly, then add 15 parts of deionized water in batches, stir thoroughly for 20 minutes to form a uniform slurry;

[0081] Step 4: Vacuum degassing: put the slurry in step 4 into a vacuum mixer, and after the vacuum degree reaches -0.1Mpa, stir for 20 minutes to remove the bubbles generated by stirring in the slurry, and then seal and store for later use;

[0082] Step 5: Pour the defoamed slurry into the silicone mold cavity treated with a release agent, and vibrate it for 10 minutes using a special vibration tool at the mold corner to expel the residual air in the mold cavity, so that the slurry is fully filled in the silicone mold and the surface is in a slurry state;

[0083] Step 6: demoulding and drying: the mold and slurry after casting are placed in an environment with a temperature and humidity of 24°C and 45% respectively to cure and harden the slurry. After the slurry is hardened, it is taken out and the silicone mold is removed. The riser tube embryo is obtained and then placed in an oven at 110°C for 30 hours to dry and remove excess moisture inside the riser tube embryo.

[0084] Step 7: Sintering of the riser tube embryo: The dried riser tube embryo is placed in a push-plate kiln and sintered at 1150° C. to obtain a ceramic riser tube for vacuum low-pressure casting of high-temperature alloys.

[0085] Example 4

[0086] A ceramic riser tube for vacuum low-pressure casting of high-temperature alloys is prepared according to the following steps:

[0087] Step 1: Prepare aggregate: by weight, take 17 parts of 5 μm alumina powder, 16 parts of 0.5 μm alumina fine powder, 38 parts of fused quartz powder with a particle size of 0.3-1 mm, and 29 parts of fused quartz fine powder with a particle size of 0-0.3 mm, put them into a mixer, stir for 15 minutes, stir the aggregates thoroughly and evenly, and set aside;

[0088] Step 2: Prepare powder: Take 2 parts of silica fume, 0.03 parts of customized boric acid particles, 5 parts of binder, and 0.4 parts of dispersant by weight, put them into a blender, stir for 17 minutes, stir the powder thoroughly and evenly, and set aside;

[0089] Step 3: Prepare slurry: put the aggregate into the mixer, slowly add the powder during the mixing process, stir for 5 minutes to mix evenly, then add 14 parts of deionized water in batches, stir thoroughly for 16 minutes to form a uniform slurry;

[0090] Step 4: Vacuum degassing: put the slurry in step 4 into a vacuum mixer, and after the vacuum degree reaches -0.1Mpa, stir for 16 minutes to remove the bubbles generated by stirring in the slurry, and then seal and store for later use;

[0091] Step 5: Pour the defoamed slurry into the silicone mold cavity treated with a release agent, and vibrate it for 6 minutes using a special vibration tool at the mold corner to expel the residual air in the mold cavity, so that the slurry is fully filled in the silicone mold and the surface is in a slurry state;

[0092] Step 6: demoulding and drying: the mold and slurry after casting are placed in an environment with a temperature and humidity of 20°C and 40% respectively to cure and harden the slurry. After the slurry is hardened, it is taken out and the silicone mold is removed. The riser tube embryo is obtained and then placed in an oven at 110°C for 25 hours to dry and remove excess moisture inside the riser tube embryo.

[0093] Step 7: Sintering of the riser tube embryo: The dried riser tube embryo is placed in a push-plate kiln and sintered at 1000° C. to obtain a ceramic riser tube for vacuum low-pressure casting of high-temperature alloys.

[0094] Example 5

[0095] A ceramic riser tube for vacuum low-pressure casting of high-temperature alloys is prepared according to the following steps:

[0096] Step 1: Prepare aggregate: by weight, take 18 parts of 5 μm alumina powder, 15 parts of 0.5 μm alumina fine powder, 36 parts of fused quartz powder with a particle size of 0.3-1 mm, and 31 parts of fused quartz fine powder with a particle size of 0-0.3 mm, put them into a mixer, stir for 14 minutes, stir the aggregates thoroughly and evenly, and set aside;

[0097] Step 2: Prepare powder: Take 4 parts of silica fume, 0.05 parts of customized boric acid particles, 4 parts of binder, and 0.4 parts of dispersant by weight, put them into a blender, stir for 16 minutes, stir the powder thoroughly and evenly, and set aside;

[0098] Step 3: Prepare slurry: put the aggregate into the mixer, slowly add the powder during the mixing process, stir for 5 minutes to mix evenly, then add 14 parts of deionized water in batches, stir thoroughly for 18 minutes to form a uniform slurry;

[0099] Step 4: Vacuum degassing: put the slurry in step 4 into a vacuum mixer, and after the vacuum degree reaches -0.1Mpa, stir for 18 minutes to remove the bubbles generated by stirring in the slurry, and then seal and store for later use;

[0100] Step 5: Pour the defoamed slurry into the silicone mold cavity treated with a release agent, and vibrate it for 8 minutes using a special vibration tool at the mold corner to expel the residual air in the mold cavity, so that the slurry is fully filled in the silicone mold and the surface is in a slurry state;

[0101] Step 6: demoulding and drying: the mold and slurry after casting are placed in an environment with a temperature and humidity of 25°C and 45% respectively to cure and harden the slurry. After the slurry is hardened, it is taken out and the silicone mold is removed. The riser tube embryo is obtained and then placed in an oven at 110°C for 28 hours to dry and remove excess moisture inside the riser tube embryo.

[0102] Step 7: Sintering of the riser tube embryo: The dried riser tube embryo is placed in a push-plate kiln and sintered at 1200° C. to obtain a ceramic riser tube for vacuum low-pressure casting of high-temperature alloys.

[0103] By carrying out a 1200°C water-cooled thermal shock test on the riser tubes in Examples 1-5 for 10 experimental cycles, cracks and bursts appeared in all the riser tubes, but the high-temperature flexural properties were different. The high-temperature flexural strength of the riser tube prepared in Example 1 was 55.2 MPa; the high-temperature flexural strength of the riser tube prepared in Example 2 was 38.4 MPa; the high-temperature flexural strength of the riser tube prepared in Example 3 was 40.5 MPa; the high-temperature flexural strength of the riser tube prepared in Example 4 was 36.7 MPa; and the high-temperature flexural strength of the riser tube prepared in Example 1 was 41.2 MPa.

[0104] According to Examples 1-5, qualified ceramic riser tubes were prepared from different raw material ratios and process parameter combinations in multiple groups of examples, proving that the preparation method of the invention is feasible, and the product quality is stable under fluctuations in key parameters, providing a reliable basis for industrial production. The ceramic riser tubes prepared in the above examples have the advantages of high temperature resistance, no reaction with alloy liquid, good thermal stability, etc., and can ensure the purity of high-temperature alloy liquid. They can be used not only for counter-gravity casting of high-temperature alloys, but also for low-pressure counter-gravity casting of high-melting-point metal materials such as cast steel and cast iron.

[0105] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0106] Although the embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and cannot be understood as limiting the present invention. Those skilled in the art may change, modify, replace and modify the above embodiments within the scope of the present invention.

[0107] The above specific implementations of the present invention do not constitute a limitation on the protection scope of the present invention. Any other corresponding changes and modifications made based on the technical concept of the present invention should be included in the protection scope of the claims of the present invention.

Claims

1. A ceramic riser tube for vacuum low-pressure casting of high-temperature alloys, characterized in that: The raw materials for making the ceramic riser tube include aggregate, powder and deionized water; In terms of weight, the aggregate comprises: 10-20 parts of alumina powder particles, 15-25 parts of alumina fine powder particles, 30-50 parts of fused quartz powder, and 15-30 parts of fused quartz fine powder; The powder material includes 1-5 parts of silica fume, 3-5 parts of binder, 0.4 parts of dispersant, 0.01-0.05 parts of boric acid; the ionized water is 10-15 parts; The diameter of the aluminum oxide powder particles is 5 μm, and the diameter of the aluminum oxide fine powder particles is 0.5 μm.

2. A method for preparing a ceramic riser tube for vacuum low-pressure casting of high-temperature alloys, characterized in that: The following steps are involved: Step 1: preparing aggregate: according to weight parts, obtain 10-20 parts of alumina powder particles, 15-25 parts of alumina fine powder particles, 30-50 parts of fused quartz powder, and 15-30 parts of fused quartz fine powder, and mix them evenly in a blender to obtain aggregate; Step 2: Prepare powder: according to weight parts, obtain 1-5 parts of silica fume, 3-5 parts of binder, 0.4 parts of dispersant, and 0.01-0.05 parts of boric acid, mix them evenly in a blender to obtain powder; Step 3: Prepare slurry: add powder to aggregate, mix well, add 10-15 parts of deionized water in batches, and stir to form slurry; Step 4: The slurry obtained in step 3 is sent to a vacuum mixer to remove bubbles in the slurry for later use; Step 5: pour the defoamed slurry into the mold cavity; Step 6: Demolding and drying: After the slurry hardens, take it out of the mold, and place the riser tube embryo in an oven for drying; Step 7: Sintering of the riser tube embryo: placing the dried riser tube embryo in a push-plate kiln furnace, and sintering to obtain a ceramic riser tube for vacuum low-pressure casting of high-temperature alloys.

3. The method for preparing a ceramic riser tube for vacuum low-pressure casting of high-temperature alloys according to claim 2, characterized in that: The particle diameter of the fused quartz powder in step 1 is 0.3-1 mm; the particle diameter of the fused quartz fine powder is 0-0.3 mm; and the mixing time of the prepared aggregate in the mixer is 10-15 min.

4. The method for preparing a ceramic riser tube for vacuum low-pressure casting of high-temperature alloys according to claim 2, characterized in that: The binder in step 2 is gel powder; the dispersant is sodium tripolyphosphate; and the mixing time of the prepared powder in the mixer is 15-20 minutes.

5. The method for preparing a ceramic riser tube for vacuum low-pressure casting of high-temperature alloys according to claim 2, characterized in that: In step 3, after adding the aggregate to the powder, stir and mix for 5-10 minutes, then add deionized water in portions and continue stirring for 15-20 minutes.

6. The method for preparing a ceramic riser tube for vacuum low-pressure casting of high-temperature alloys according to claim 2, characterized in that: In step 4, during the defoaming process using a vacuum mixer, the vacuum degree is -0.1Mpa and the vacuum defoaming time is 15-20 minutes.

7. The method for preparing a ceramic riser tube for vacuum low-pressure casting of high-temperature alloys according to claim 2, characterized in that: The mold in step 5 is a silicone mold; the defoamed slurry is poured into the silicone mold cavity treated with a release agent, and a vibration tool is used to expel the residual air in the mold cavity.

8. The method for preparing a ceramic riser tube for vacuum low-pressure casting of high-temperature alloys according to claim 2, characterized in that: In step 6, the slurry is taken out from the mold after hardening, and the riser tube embryo is placed in an oven for drying, which specifically includes: placing the cast mold and the slurry in a constant temperature and humidity chamber for curing and hardening, and the temperature and humidity of the constant temperature and humidity chamber are 20-25°C and 40%-45% respectively; after the slurry is hardened, it is taken out from the mold, and the riser tube embryo is placed in an oven for drying, and the drying temperature is 110°C and the drying time is 20-30h.

9. The method for preparing a ceramic riser tube for vacuum low-pressure casting of high-temperature alloys according to claim 2, characterized in that: In step 7, the sintering temperature of the riser tube embryo is 1000-1200°C.

Images